President Donald Trump is headed for a head-to-head with America’s allies at a Group of Seven summit this week, with the European Union and Canada threatening reciprocal measures unless he reverses course on new steel and aluminium levies. An all-out trade war may become inevitable if he doesn’t. Meanwhile, the Trump administration is facing a warning from China that it’ll end negotiations to resolve trade tensions if the U.S. follows planned tariffs on China. The White House appeared unfazed by threats from allies and China.